Shielding gas plays an important role in producing a quality weld. Specifically, the shielding gas prevents, or shields, the weld from atmospheric oxygen, which would cause oxidation, and other atmospheric contaminants. Accordingly, maintaining a desirable flow of shielding gas through a welding device is important to ensure that a quality weld can be produced. For example, it is desirable that the shielding gas exiting the nozzle of the welding device has a laminar, as opposed to turbulent, flow profile because a laminar flow profile introduces less undesirable reactive gases from the atmosphere into the inert gas column shielding the weld area.
It is also desirable that the shielding gas maintains a laminar flow profile even at a relatively significant distance from the nozzle orifice, i.e. that the shielding gas column has a relatively long laminar flow profile. This allows the welding device to be operated with the tungsten electrode extending (sticking out) further from the end of the nozzle to improve visibility and accessibility to the weld area, which allows for a user of the welding device to more effectively weld tighter or difficult to reach joints. For these reasons, higher quality and more easy to obtain welds may be achieved where the flow rate of shielding gas in a welding device is maintained at a level that provides a shielding gas column having a laminar flow profile.
Despite the importance of maintaining and setting proper shielding gas flow rates, conventional welding devices contain few shielding gas flow controls. Specifically, there is little guidance provided to a user regarding what flow rate to initially set for the shielding gas. Rather, the flow rate used during a weld is typically dependent on the user's particular experience and understanding of how to obtain a desirable shielding gas flow profile, and thus is subject to user error. Moreover, there is little control over the flow of the shielding gas once the initial flow rate is obtained.
Conventional weld devices often rely on a ball float valve, in which the height of a ball float serves to identify the flow rate of the shielding gas. However, these conventional arrangements suffer from a number of drawbacks, examples of which are described below. First, identifying the flow rate set point on ball float flow is often difficult. Various manufactures use different locations on the ball relative to the float tube scale to indicate flow rate. Measurements taken from the bottom, middle, and top of the ball are most common. Second, in order to set the flow rate of a ball float valve, gas must be flowing. This requires the user to turn on the gas flow while setting the flow rate. The user must initiate gas flow, typically from the welding power source or a valve on the welding torch, before adjusting the flow rate. This process is both cumbersome and wasteful.
Third, access can be limited or difficult by the fact that the ball float valve is typically located at the shielding gas manifold, which may be positioned a great distance away from the user and the weld area when the welding device is in use. Fourth, in large arrangements with numerous valves and poor hose management, identifying the correct ball float valve controlling the flow rate of a specific welding power source can be difficult. As a result, an operator could accidently adjust the gas flow rate for a welding power source other than intended. Fifth, a ball float does not maintain a constant flow rate with varying pressure upstream or varying head loss downstream of the ball float valve. In the case of a low shielding gas bottle or manifold pressure below the pressure regulated for the ball float, the flow rate will drop below the initial set point providing inadequate gas coverage and decreased weld quality.
Embodiments of the present invention provide a shielding gas flow control system that provides a user with greater control over the flow profile of the shielding gas in a welding device.